Hydraulic brake



R. c. RiKE HYDRAULIC BRAKE Oct. 10, 1939.

' Fild Aug. 25, 1937 Patented Oct.' 10, 1939 PATENT OFFICE Richard C. Bike, Dayton,

eral Motors Corporation, Detroit, Mich.,'a corporation of Delaware Ohio, assignor to Gen- Y Application August 23, 1932, Serial No. 160,388

3 Claims.

This invention relates to brakes and particularly to hydraulicY operating mechanism by means of which fluid is transmitted from a master cylinder for applying Vthe brakes at the wheelsof the 6 vehicle.

An object vof the invention is an improved master cylinder and installation thereof.

A further Objectis to provide a master cylinder assembly wherein a-progre'ssive mechanical ad- 10 vantage is provided.V v

A still further object `is the provision of a master cylinder assembly wherein the pedal is associated therewith in a way to utilize the first part of the pedal movement to take up brake ll shoe clearance, vthe pedal thereafter acting with an increasing mechanical advantage to supply the greater force necessary to retard the rotation of the drum engaged by the shoes. l Among other objects are eflciency in operation and economy inV manufacture.

Still other objects will be appreciated from the following description.

In the accompanying drawing: Figure 1 is a view in elevation of the assemv bly including the master cylinder andthe operating partsassociated therewith.

Figure 2 is a section on line 2-2 of Figure 1. Figure 3 is a section on line 3-3 of Figure 1. Figure 4 is a section on line 4'-4 of Figure 3. Referring byreference characters to the drawing the door board of a motor vehicle is represented by numeral 1 and at 9 is seen a curved rod terminating in a foot pad II. The parts 9 and II constitute a pedal for applying the brake. Beneath the floor board 1 Ais a channel-shaped bracket I3, the base of which is secured by suitable fastening means I5. The side Walls l1 and I9 of the bracket are of triangular shape as shown by Figure 1. A shouldered pivot bolt 2| vextends through wall I1 and is held in position by a nut `23. Pivoted on this bolt is an arm 25. To the end ofthe arm is secured the end of the arcuate rod 9 as at I0. To arm 25 at a point near its connection with the curved rod 9 is a shouldered pivot 21 secured thereto by a rnut 29. A piston rod 3l is rotatably supported by pivot 21. Piston rod 3l is slidably mounted in a piston 33 reciprocable within a cylinder 35. The latter may have a liner of rub- 50 ber or the like 31 to serve to centralize the piston. 'I'he cylinder 35 is threaded into a cross head 39, the latter having a trunnion 4I extending through wall I1. The trunnion is surrounded by a spacing collar I3 engaging the wall I1 and a shoulder 45 on the trunnion. The collar -piston 33. A closure 59 is secured to the upper This closure is apertured for l0` end of cylinder 51. the passage of piston rod 3l and carries asuitable sealing device 6I.

At 63 is another cylinder secured to the cross head and in axial alignment with cylinder 35. Its lower end is threaded and to it is secured an ap- 15 ertured closure 64 to which a conventional conduit 56 isattached. If so desired a valve constructlon represented as a Whole by numeral 65 and for which no invention is'herein claimed, may be used at the end of cylinder 63. This 20 valve opens to permit discharge of iiuidv from cylinder 63 and will open to yadmit a return of uid to said cylinder when the pressure of said uidis suillcient to overcome a spring 61, the springengaging the valve at one end and the 25 piston at its other end. The annular space between cylinders 51 and 35 serves as a uid reservoir.` One or more recesses 1I are cut in the end` of cylinder 35 communicating by means of an axial channel 13 with the reservoir. 'I'his is 30 best shown in Figure 4 where the piston is shown in a position where its movement is just about to close the communication between the reservoir and the interior of 'cylinder B3. Between the seal 53 and the top of cylinder 63 the cross head 35 has a radial passage 15 communicating with an axial passage 11. This latter passage is in communication with the reservoir by means of a reduced passage 19 normally closed by a ball valve 8| seated by a spring B3 held in abutment 40 with a removable plug 85.' Figure 4 shows the piston in its retracted position. When it ad-. vances it moves through seal 53 and reduces the capacity of cylinder B3. It thus forces uid out from said cylinder 53 into the conduit 66 by 45 means of which the brakes .are applied in the usual way. In doing so, sucient pressure is built up in cylinder 63 to supplement the action of spring 83 and hold ball valve 8| closed. Also the first movement of the piston fully closes the communication between the reservoir and the cylinder Vby Ways of passages 1I and 13. When the piston returns after brake application the tendency of suction to develop in cylinder 63, if the piston 33 returns faster than the brake shoe 55 retraction spring restores fluid to this cylinder, is overcome by passage of fluid from the reservoir entering the cylinder 6l by way of valve II. When the piston 33 is fully retracted any excess of fiuidfdelivered to the cylinder 63 by the completion of the return ilow may reach the reservoir by way of passages 1l and 13.

The full lines of Figure 1 show the mechanism in brake released position. The dotted lines represent the parts in brake applied position. The arrangement is such that for equal increments of pedal depression the corresponding axial movements of the piston progressively decrease. In consequence the brake shoe clearances are quickly taken up, the pedal acting with a relatively low mechanical advantage. "By the time that the shoes engage the drum and when greater forces are required to check the rotation oi the drum the parts have assumed positions where the movement of the piston is very slight for the corresponding movement of the pedal and the pedal thus acts with a high mechanical advantage. In consequence, no great effort is required to secure eieetive braking action. It will be appreciated that the pinion trunnion 4i may be located as desired relative to pin 2l to secure just the kind of mechanical advantage desired.

I claim:

1. For use with a hydraulic operating system,

a master cylinder, a pedal spaced pivots for said cylinder and pedal, said cylinder having a piston rod reciprocable therein, and pivot means directly connecting said piston rod and pedal and said pivot means being movable in response to movement of saidpedal toward a position oi alignment with said pivots.

2. In hydraulic operating means for vehicle brakes, a bracket fixed to said vehicle, a lever provided with a pad, the lever and pad constituting a pedal, a pivot between said lever and bracket, al master cylinder having a piston, a second and spaced pivot whereby said master cylinder is pivoted to said bracket, pivot means directly connecting said lever and piston of said master cylinder, said pivot means being movable about the pivotal center of the lever, along the axis of the piston rod and toward a position of alignment with said pivots, the location o! said spaced pivots being such as to give said pedal a variable mechanical advantage in projecting said piston into said cylinder.

3. For use with a hydraulic operating system, a master cylinder, a manually operable member, spaced pivots for said cylinder and member, said cylinder having a piston rod reciprocable therein, and pivot means directly connecting said piston rod and said member, said. pivot means being movable in response to movement of said member toward a position of aligment with said pivots, together with a reservoir of annular form secured to and in co-axial relation with said master cylinder, said piston rod extending through said reservoir.

RICHARD C. RIKE. 

